The background of this invention relates to the packing and processing of comestibles such as food and beverage in containers having a seam along one interior side surface. In particular, such containers are usually coated 3-piece cans in that they are constructed from a cylindrical hollow open ended body and two circular ends. Three-piece containers are fashioned from flat blanks of metal sheet stock which are rolled into a cylindrical form and along a longitudinal side are sealed by soldering, by bonding, by cementing or by welding. Such flat strips of metal are heavily treated to resist corrosion by application of tin, chromium and/or organic coatings. Such treatments protect substantially the entire inside and outside surfaces of the 3-piece container body. The formed cylindrical body has two open ends which are completed by circular bottom and top closures and which are also precoated and/or plated.
During the formation of such a container, the side seaming operation is such that a raw edge or raw metal is exposed to the inside of the container. Such a raw or untreated surface must be protected by a post forming coating operating in order to assure proper conditions for the ultimately packed and processed comestibles. In the past, raw inside surfaces of a container were covered by materials such as solution vinyl stripe coatings which tend to run off sharp raw edges, sag and drip. Consequently, high coating weights or multiple layers of coating were required in order to provide adequate coverage. The heavier coating required longer and/or higher curing times and temperatures in order to remove the solvents. Sometimes total removal of solvents was practically impossible resulting in internal contamination of the packed and processed comestibles giving an off-flavor to the product. While the surface finish of the seam is a function of the manufacturing process used to generate it; such seams need internal protective covering over any exposed raw metal.
In order to overcome the problems with the prior solution stripes, it is an object of the present invention to provide a material which upon application forms a gel structure which adheres across the rough internal surface presented by a manufactured seam.
It is a further object of the present invention to minimize the coating weight and thickness of such repair seams.
It is a still further object of the present invention to provide an internal surface repair coating which requires a minimum amount of energy for purposes of curing.
It is a final object of the invention to provide a low cost, reliable and effective internal raw surface protection coating for a 3-piece comestible container.